Plastic containers are in widespread use in the food industry and typically include a lid and a base, hingedly connected along one edge, allowing the container to be opened and closed repeatedly to access the contents. One example is a plastic egg carton, wherein the hinge allows eggs to be selectively retrieved from the container without risk of dropping or misplacing the carton lid. The hinge also assists in guiding the lid into a closed and secured position.
Egg cartons are commonly composed of plastic materials as plastics are non-absorbent and allow for inexpensive and rapid mass production while also allowing various structural reinforcing elements to be included in the carton's construction. The hinge is commonly provided as part of a peripheral flange on the carton perimeter for ease of manufacturing as well as the added rigidity a flanged hinge brings to the egg carton. The increased rigidity of the carton reduces the risk of the container collapsing when in a vertically stacked configuration and reduces the risk of the eggs breaking due lateral forces applied to the container (e.g., when a consumer grabs a closed container in one hand and squeezes inwardly). In these cases, however, the corners (trim edge configuration) of the flanged hinge can pose a safety hazard to users due to the corners presenting sharply angled and exposed plastic edges (see e.g., the sharply angled edges at each end of the hinge in the prior art cartons of FIGS. 1A and 1B). Manufacturing the trim, at the ends of hinge, so that it presents rounded corners when the egg carton is closed presents manufacturing difficulties. Bringing the hinge flush with the external walls of the carton may greatly reduce the structural rigidity of the package and/or provides a generally less appealing aesthetic than a flanged hinge.
Thus there is a need to manufacture a hinged plastic container, such as an egg carton, that is less likely to harm a user handling it, while still maintaining the structural and aesthetic advantages of the flanged carton.